Electric arc and method of producing same



Dec. 4, 1934. Q 5 ASHCRAFT 1,983,430

ELECTRIC ARC AND METHOD OF PRODUCING SAME Filed April 16, 1954- ,I 5 1 .4 g :wcxxama ,4

y /4 i V 63 '83 [NVf/VTOR CLARNC 8 AJHCRAFT A r TOR/YE)? Patented Dec. 4, 1934 UNITED STATES ELECTRIC ARC AND METHOD OF PRODUCING SAME Clarence S. Ashcrait, Los Angeles, Calif. Application April 16, 1934, Serial No. 720,762

12 Claims. (Cl. 176-52) .My invention relates to an electric arc and a method of producing same and is of utility in motion-picture projectors, search-lights, etc.

- In the art to which this invention appertains,

it is common practice to provide an arc or flame by sending an electric current of suitable voltage through a pair of carbons which are disposed with their ends adjacent to each other, thus producing a flame or flames between the ends of these l0 carbons.

There are in general use at the present time two 'typesof electric arcs, one the so-called low intensity are and the other the so-called high-intensity arc such as is disclosed in the patent to :15 Sperry for Method of operating flaming arc lights for projectors, No.'1,22'1,210, issued May 22, 1917. The low intensity arcs have great economy and low maintenance costs but the light produced thereby is of a yellowish color and is therefore not well suited for use in motion-picture projectors, in which art my invention is of particular utility.

The so-called high intensity are produces good screen illumination but has certain disadvantages. In the first place, the maintenance costs are very high. Due to high amperage and voltage the carbons burn very rapidly, and, furthermore, there is a relatively high cost in the replacement of parts which quickly deteriorate due 80 to the'high intensity operating conditions of such arc. Furthermore, the operating costs are relatively high by reason of a high power consumption; Although this so-called high intensity are produces good illumination, the light is of a bluish white color which is better adapted for motion-picture projection work than the yellowish colored light produced by the so-called low intensity are, it is not, however, the most satisfactory light.

. 40 It is an object of my present invention to provides; method of producing and operating a socalledhigh intensity electricarc in which excellent illumination or light intensity is attained, in which there is great economy by reason of low 5 carbon consumption, in which the maintenance costs are low because the replacement of parts is less frequent, in which the operating costs are low due to a relatively low power consumption, and in which the light produced thereby is of a pure white color.

It is an object of my invention to provide a method of producing or operating an electric are which will produce a white uniform shaft of light 5 which is particularly suited for motion-picture projection work.

Another object of the invention is to provide amethod of producing an electric arc in which apositive flame of luminescent gas is substanmo tiaily flattened adjacent the positive crater such that the flattened portion substantially complete- 1y covers the area of crater.

Another object of the invention is to provide a method of producing an electric arc in which the luminescent gas of the positive flame is in contact with substantially the entire area of the crater.

Another object of the invention is to provide a method of producing an electric arc in which a positive flame of luminescent gas is mushroomed by a negative flame.

Another object of my invention is to provide a method of producing or operating an electric are which will produce an are or flame which has a substantially symmetric or concentric luminescent area.

It is another object of my invention to provide -a method of producing an electric arc in which luminescent gas of the positive flame of the arc is caused to flow evenly from the crater of the positive electrode and is then flattened to provide a symmetric or concentric luminescent area.

Another object of my invention is to provide a method of producing an electric are m which i a negative flame is directed against a positive flame to produce a body of lumniscent gas having a'substantially flattened surface and having its periphery extending rearwardly and surrounding the end of the positive electrode.

It is a further object of my invention to provide a method of operating an electric arc in which the crater of the positive electrode is of substantially isotemper'ature.

A still further object of my invention is to provide a method of producing an electric arc in which the crater of the positive electrode burns evenly and therefore requires no rotation.

It is a still further object of my invention to provide a method of operating an electric arc in which the electrodes are in axial alignment, in which the positive and negative flames oppose each other.

Other objects and advantages of my invention will be pointed'out in the following description.

For the purpose of explaining my invention to thoseskilled in the art in order that they may practice the same, I will describe in detail a method of the preferred form of my invention. In the description which follows I will describe the details of construction of the carbons employed, the dimensions of the parts, spacings, the current flow, and voltage, as well as other definite qualities and quantities which are involved in the performance of the preferred form in the preferred process of my invention.

It should be strictly understood that by choosconstrued in accordance with the preceding statement of invention of this application and the appended claims, to cover any and every process which comes within the broad scope of myinvention and utilizes the principles thereof.

For the purpose of assisting in the explanation,

reference will be made to the appended drawing in which there is shown the carbons which are employed in practicing the preferred embodiment of my invention and the electric arc which is produced by the preferred method of my invention. I shall now refer to the drawing in detail and describe the preferred method of 'my invention.

The numeral 11 is a positive electrode, and the numeral 12 is a negative electrode, both of which are carbon and preferably copper coated as at 14. The positive electrode has a core 15 composed of a material which during operation produces a brilliant gaseous positive flame. The negative electrode has a core 16 of arc-sustaining material. The positive electrode is '7 mm. in diameter, and the negative electrode is 6 mm. in diameter. The two electrodes are in axial alignment on the axis AA. During operation the positive electrode is formed with a crater 17 which is about .245" in, diameter, and the negative electrode is formed with a rounded end 18. The dis tance between the ends of the electrodes, as indicated at B, is A" and is maintained approximately thereat during operation by manually or automatically operated means.

This is the construction of the positive and negative electrodes which I prefer to use in practicing my invention. Obviously, as aforesaid, my invention is not limited to this particular apparatus. V

In practicing my invention, the electrodes are connected in a direct current electric circuit capable of providing the required current and voltage. To start the arc, the electrodes are moved into contact and are then returned to the desired spaced position.

The negative flame 20 which is of relatively even density issues from the rounded end 18 of the negative electrode 12 substantially concentric to the axis AA and diverges toward the positive electrode 11, and has a substantially frusto-conical shape. In this embodiment the angle between the sides of the negative flame 20 is substantially 69, which due to the upward draft produced by heat is substantially 36' above and 33 below the axis AA.

If there is no crater 17 in the end of thepositive electrode when starting the method, the core 15 will burn away and form a crater.

The positive flame 21 is formed in the crater 17. It consists essentially of the gas formed by the burning of the core 15 and is highly luminescent.

This flame issues from the crater and toward the negative electrode. The two flames meet at line 23 and the positive flame is flattened into a disc which is substantially concentric to the axis AA and is approximately 5%" in diameter. The peripheral portion, when conditions are most desirable, is forced rearwardly as at 24 so as to surroundthe end of the positive carbon, and is useful in adding heat to the end of the positive carbon so as to produce an isothermal condition in the walls forming the crater. This is of assistance in producing an evenly distributed issuance of luminescent gas from the crater.

In practicing my invention, I find that the current density must be high enough to produce the luminescent gas in a volume which will issue from the crater and at the same time must be below the point where the pressure of the negative flame against the positive flame will.tend to break through or destroy the luminescent disc. For example; in practicing my invention with the sizes and construction illustrated in the accompanying drawing, the luminescent gas does not form in desired quantities until the current flow is approximately 40 amperes. As the current flow is increased, the volume of luminescent gas which is produced is increased; and also the pressure of the negative flame is increased. During this increase the negative flame pressure appears to gradually build up to the point where the positive flame is flattened into a disc. It appears from observation that the positive flame at this point is not forced back around the positive electrode as at 24; however, the luminescent area is present in the form of the concentric disc and produces the positive flame, and the results obtained are in- .2.

ferior to those obtained at lower current flows. With the apparatus disclosed I have operated with a current as low as 40 amperes and as high as 65 amperes; but the best results, such as is illustrated in the accompanying drawing, were obtained with a current of 46 amperes and a gap voltage of 36 volts.

By the term luminescent gas as used in the claims is meant any gas giving a brilliant flame and includes a gas in which incandescent particles may be present.

I claim as my invention:

1. The method of producing an electric arc in an arc lamp which comprises forming luminescent gas in a crater of a positive electrode in such volume that it issues outwardly therefrom, and directing a flame from a negative electrode against said luminescent gas so as to produce a body of luminescent gas having a substantially flattened surface, the periphery of said body extending rearwardly to form a portion completely surrounding the end of said positive electrode.-

2. The method of producing an electric arc in an arc lamp which comprises forming luminescent gas in a crater of a positive electrode in such against said luminescent gas so as to produce a body of luminescent gas having a substantially flattened surface, the periphery of said body extending rearwardly to form a portion completely surrounding the end of said positive electrode and substantially concentric therewith.

3. A method of producing an electric are which comprises placing a positive electrode, having a core capable of forming a flame of luminescent gas in said arc, adjacent a negative electrode, forming a crater in said positive electrode, directing a flow of luminescent gas outwardly therefrom and toward said negative electrode, and directing a negative flame against said luminescent gas to form a flame having a substantially flattened surface opposite said negative electrode and to cause said luminescent gas to flow outwardly and rearwarllly so as to form a portion completely surrounding the end of said positive electrode.

4. The method of producing an electric are which comprises positioning a positive electrode, capable of emitting a positive flame of luminescent gas, adjacent a negative electrode, causing a current to flow between said electrodes sufllcient to form said luminescent flame and a negative flame, directing said negative flame against said positive flame in such a manner as to form a crater in said positive electrode and substantially flatten a portion of said lurninescent flame so as to form a substantially flattened luminescent surface in front of the crater, whereby the crater is substantially'completely covered by said flattened portion of said luminescent flame and said luminescent gas contacts substantially the entire area of said crater,

5. The method of producing an electric are which comprises positioning a positive electrode, capable of emitting a positive flame oi luminescent gas, adjacent a negative electrode, causing a current to flow between said electrodes sumcient to form said luminescent flame and a negative flame, directing said negative flame against said positive flame in such a manner as to form a crater in said positive electrode and substantially flatten the surface of at least a portion oi said luminescent flame so that the area of said flattened surface exceeds the area of the crater projected axially oi the positive electrode upon said flattened surface, whereb the crater is substantially completely covered by said flat tened portion of said luminescent flame and luminescent gas contacts substantially the entire area of said crater.

6. The method of producing an electric are which comprises positioning a positive electrode, capable of emitting a positive flame of luminef cent gas, adjacent a negative electrode and sub stantially coaxial therewith, causing a current to flow between said electrodes sumcient to form said luminescent flame and a negative flame, directing said negative flame against said positive flame insuch a manner as to term a crater in said positive electrode and substantially flatten a portion of said luminescent flame so as to for l a substantially flattened luminescent surface front oi the crater, whereby the area or no crater is substantially completely covered by so flattenemportion of said luminescent flame said luminescent gas contacts substantially the entire area of said cra er,

'3. The method of producing an electric are which comprises maintaining an arc across a ,gap of approximately of an inch between positive electrode, capable of forming a positive flame oi luminescent gas, and a negative niec trode, causing sumcient current to flow to form said luminescent flame and a negative flam directing said negative flame against said pot tive flame in such a manner as to term a ore. to in said positive electrode and substantially a portion of said luminescent flame so as to a substantially flattened luminescent surface l'ront oi! the crater, whereby the area of crater is substantially completely covered by said flattened portion of said luminescent flame said luminescent gas contacts substantially the entire area of said crater.

8. The method oi producing an electric which comprises positioning a positive electrode,

capable of emitting a positive flame oi luminescent gas, adjacent a negative electrode, said electrodes being substantially the same diameter, causing a current to flow between said electrodes suflicient to form said luminescent flame and a negative flame, directing said negative flame against said positive flame in such a manner as to form a crater in said positive electrode and substantially flatten. a portion of said luminescent flame so as to form a substantially flattened luminescent surface in front of the crater, whereby the area of the crater is substantially completely covered by said flattened portion of said luminescent flame and said luminescent gas contacts substantially the entire area of said crater.

9. The method of producing an electric are which comprises positioning a positive electrode, capable oi emitting a positive flame of luminescent gas, adjacent a negative electrode, causing a current of approximately 40 to 65 amperes to flow between said electrodes in order to form said luminescent flame and a negative flame, directing said negative flame against said positive flame in such a manner as to form a crater in said positive electrode and substantially flatten a portion of said luminescent flame so as to form a substantially flattened luminescent surface in front of the crater, whereby the area of the crater is substantially completely covered by said flattened portion said luminescent flame and said luminescent gas contacts sub stantially the entire area of said crater.

iii The method oi producing an electric are which comprises positioning a positive electrode, capable oi emitting a positive flame of luminescent gas, adjacent a negative electrode, forming a crater in said positive electrode, forming said flame of luminescent gas in contact with substantially the entire area of said crater, substantiaily flattening at least a portion of said flame adjacent said crater, and maintaining said flattened portion in a position to substantially cornpletely cover the entire area of said crater.

ii. The method oi producing an electric are which comprises positioning a positive electrode, capable of emitting a pos Lve flame of luminascent gas, adjacent a negative electrode, causing a current to flow between electrodes sufflcient to form said luminescent flame and a negative flame, lesions the pressure of the negative flame e pressure of the positive flame so as to form crater said positive electrode with said luminescent flame in corn tact with substantially the entire area of the crater so as to substantially flatten the surface of said luminescent flame and maintain said flattened surface front or said crater so that the projection of said crater area axially of said positive electrode falls substantially completely within the margins of said flattened surface.

12, Tire method of producing an electric are which comp ises positioning a positive electrode, capable emitting a positive flame oi luminescent gas, adjacent a negative electrode, causing a current to flow between said electrodes sufll cient to form luminescent flame and a negative flame, and directing negative flame against said positive flame so as to cause the post tive flame to mushroom CLARENCQ 

